Optoelectronic components or active optical devices such as diode lasers, light-emitting diodes (LEDs), and photodiode detectors are used for printing, data storage, optical data transmission and reception, laser pumps, and a multitude of other applications. Most optoelectronic components are typically sealed inside a hermetically sealed package for performance requirements and operational stability. Optoelectronic packages are intended to provide a hermetic structure to protect passive and active optical elements and devices as well as related electrical components from damage resulting from moisture, dirt, heat, radiation, and/or other sources.
For high-speed applications (e.g., 1 Gbps and above), proper operation of the optical and/or electrical components inside the package may be affected unless careful attention is paid to the packaging of these components. Standard optical module packaging such as that used in optical telecommunication applications requires a hermetic enclosure. Sealed packages are necessary to contain, protect, and electrically connect optoelectronic components. These requirements have resulted in packages that are large, costly, and more difficult to manufacture than typical electronic packages. In fact, the size cost of most optoelectronic devices are mainly drive by the package rather than the optical devices themselves.
Current designs of optoelectronic packages and associated fabrication processes are not easily adapted for automated manufacturing techniques because conventional packages for optoelectronic components such as large so-called “butterfly” packages are characterized by numerous mechanical parts (submounts, brackets, ferrules, etc.), three-dimensional (3D) alignment requirements, and poor mechanical stability. Butterfly packages are basically can-and-cover type arrangements that contain an optical assembly mounted to a metallic baseplate, with leads coming out of the sides for electrical connections. The optical assembly may be built up separately, outside of the can, and then later installed inside the can. The circuits within the optical assembly are wire-bonded to the leads of the butterfly can, which is then sealed with a lid to create a hermetic enclosure. Conventional butterfly cans are bulky, costly, and time-consuming to manufacture. Further, the electrical components require a separate subassembly that is located outside of the butterfly can.
Transistor-Outline (TO) packages are also commonly used to house optoelectronic components. Conventional TO packages include a generally cylindrical metal cap and a metal header or base, to which the metal cap is attached. In such packages, metal-based bonding techniques such as, for example, brazing or fusion welding, are often required to provide a hermetic seal between the metal cap and the header. To weld the metal cap onto the header, the header is typically formed of a metallic material such as Kovar™ or stainless steel. However, it is advantageous to use ceramic bases in connection with high-speed applications because ceramic bases are ideal for RF applications. Specifically, ceramic headers provide easy routing of high-speed circuits. Because ceramic is not compatible with metal with regard to weldability, it has not been widely used as the material of construction for the header or base in conventional TO packages. A new family of TO headers which have a ceramic base with a weld ring may also be used for high speed applications.
Conventional TO packages for receiver optical sub-assemblies (ROSA) and transceiver optical sub-assemblies (TOSA) are typically large and result in the photodiode chip being spaced apart from the end of the fiber stub by a distance ranging from about 2 to about 3 mm. This large spacing is required because a cap structure is conventionally used to enclose and hermetically seal around the photodiode chip which is disposed on a metallic or ceramic base. The cap structure enclosing the photodiode chip includes a lens disposed in its top wall that must be aligned precisely with the fiber stub. The fiber stub is accommodated within the fiber receptacle which is either welded or epoxied onto the lens cap.
The manufacture of the ROSA is essentially a two part process that requires precise alignment of the cap and the fiber receptacle. Thus, an error in any one of these attachment steps will result in a defective product. As a result, the process is inefficient, time consuming and costly. Further, the fiber stub is disposed a relatively large distance from the photodiode chip, typically between 2 and 3 millimeters, which results in a package that is quite large thereby limiting its applications.
Therefore, there is a need for improved optoelectronic packages and processes for manufacturing optoelectronic packages that can address some or all of the problems described above.